Telephone system



R. C. DAVIS Y TELEPHONE SYSTEM June l 1926. 1,586,520

Filed May 5,. 1924 by Affa- PetenteclA .lone 1 1926.

RICHARD cgnAvs, OFNEW Yon-x, N, Y., .Assxeiqoe To WESTERNErirotio'ooivrfrinm INCURPURATEQ oF NEW Ydmc, N. Y., 'A COBPoRATIoNfoFNEW Yong.

` mamme-NE 's-serein. y

, kApplwenn mea my 5,

This rwentifoi.v relates @to telephone ex# change systems and, moreparticularly yto common battery Systems in which connecting:oisrcuitserelused in` extending V@alle from Galline to' a @allee um. -f1 s Th-o' object iothis Viaxyentifoxiis to provide j im improved andsimplied connect-ing `oircmit o'r suoli :systems'fbymeens fof `which thef eeiyfce Fis greatly improved o @ne of the vfesjutu'res of theinvention is ftlie`, kv

provision elf Vve. sifmplied Ycenaiectirig*circuit of the :abovecharecterfwhereby the suppli- Another feature ofjtllieilyeit onV resides`in the proV-isionofnewn-s whereby-when the receiver :et the callingstation" Elias been re- Stoned and subseqiietlyremoved from theswitcjliliook, e "circuit interrupting `device 'is brotxglitbnto`oppearetw'e relation with asu# pei-visery signal l.to cause seidsignal' to 4flash :his clirmueterilstie marmer; This is confuio'ni l l:i :ceiling sobscriloer and mi .Another feature olfthe ifvei'ltion isfthe provision of mi. improved, calling supervisory controla/circuitwhereby the callin-g supeiyisoiy signal-associatedvsi'i'tll,the/5021.11-v ing endof the lilik circuit. isdise'bled n1-ref`spense to the essooie-tien of the goemiectifng ci cult with the calling.line #and is main-v,

mined; disabled 'Until thefcaldled subscriber lizis'answered andreplaced hisyreceiver on theswftclgllaook. n v

@ther features will beapperent from the fcllowfing de'asoiipton'` andappended, claims.. Renfelfring tothejdrawng, ,A designates 'e caliledsubscribepreseiit invention, used to interconnect the 1 subscribersr'lines for conversation. T :partelly represents a trunk llne toWhiclmrtlie" cord C may be also connected for ext-ending;

e, call to e dstantsubfscrleer .atso'me other exchange. Associatedwithlk the oord circuit is'e four party selective ringing-system.-

Assuiiiing' that subscriber A Wishes to `con- `verse' Wthfsubscriber M,-A will signal the en the operator- Will yinsert the .answering plugof'ftlie cold oirct-G vinto Vthe yjee-le aslsocated: with AslineTthereupon completing' v reuit'forrthe lightngof lamp 2, and

'tferfeteY c(interetL to .establish .rumene 1 i circui 1924.A Aserial711,034.

from groiided battery through -ftlie filament o supervieory lem-p2,yrelay y1 nd lthence to' grou-nd yover the sleeve of the callin-gl line.

Reiley 1li-1,1y Opeiltillgclosesecircuit 'for relay@ Wlrih v12m-nfbeftritojed from, grounded battery at 4relay), `right hand Winding ofrel-ay 3 5 normal contacts` of listerling; key 23.,

'midle lterna-te'fconteots of relay 1f `end im Obvious oirout for "theAoperation"of 'ie'lay middle alternate oon-'cachot relay l and; the'omtegrnlet lmndmormal contee-tof krelay;.El

4 wider control of relay L hefoperetoiiwof Yreley Belso' openedffat 4itsinerflefth-nd s normal-contact the battery connect-ien vto kthe relayscorrespondingto `relay S 'mi other` `cord. kcircuits at thesemeKVlposition. Tli-,is'preveiits 'ted- 'eiyjothfer eordfcircuit from -Vbeingconi-i tot-heoperetors telephone-set and falso i@- mits the operaito, toput up` 'other oord cirgrounded battery cuits for succeedingfoallsfwlile sles een# f neoiedand talking with e calling subsorbe'i for.relay 6 wliclimey Jetraced frere grounded better-yi, Windingoff"rels'ry-,L inner leftyliandnorml contacts o,;1"eley Slendtlieuc'etof .'grend et4 rel-ay 3 overgtli-elefti11- ope'retng associates tliemaster' ringing equipment with the" cord circuit zihdesteblislies e4`oircuit for relay 9 which may be crecedvfrom groindftlirough thewin-diiig of l lil? relay 9, conductor 211, contacts 25 of relay G,conductor 25, right hand normal contact ot' relay 8 and thence togrounded battery through the Winding of relay 8.

Relay 9 operates in this circuit and lights the ringing pilot lamp 10 inan obvious circuit. Relay 8 which is in series with relay 9 does notoperate, however, due to the high resistance Winding or" relay 9 ivhchdoes not ,breaking the locking circuit for relay 3 and permitting it torelease. Key 23 looks and remains operated until such time as theoperator desires to release it and reconnect her telephone to thisparticular connection. The release ot relay 3 causes the release ofrelays 6 and 9.

The operator is now free to answer other waiting calls.

It, however, the operator receives the desired number from the callingsubscriber she plugs the calling end of lie-r cord into the desired linewhereupon relay 5 energizes and operates in series With the supervisorylamp 3() over a path which extends from grounded battery through thelilament of lamp 30, ivindingof relay 5 and thence t-o ground over thesleeve of the called line. Supervisory lamp 30, however, does not lightin this circuitl as it is shunted through the resistance 11 to batteryat the outer alternate contact of relay 6. Let it be' assumed that the Mparty on the called line is desired, in which case the master ringingkey M Would be depressed, thus causing relay 12 to be operated in anobvious circuit. Relay 12 in operating closes a circuit for theoperation of relay 1li Which can be traced from grounded battery overthe outer lefthand alternate contacts of relay 1, conductor 52,conductor 36, Winding of relay 111, conductor 32, contacts 31 of relay 6and thence to ground through the inner right hand alternate contacts ofrelay 12. The operation of relayl 12 also causes the opf eration ofrelay 8 in an obvious circuit. Re-

lay 8 in operating locks itself up to ground over the contacts of relay5, which relay remains operated during the time the calling plug is inthe jack of the called line. Relay 8 in operating also opens theoriginal operating circuit for relay 6 but closes at its inner lett handalternate contact a holding circuit for relay 6 which can be traced fromgrounded battery through the Winding of relay 6, inner lett handalternate contacts 25 of relay G and thence to ground through theoutermost right hand alternate contacts of relay 12. In addition relay 8also opens the operating circuit for relay 3 at its outer left armature,thereby causing the release of relay 3 which relay in releasingdisconnects the operators telephone from the cord and closes a batterycircuit to other relays in the position corresponding to relay 3. rEheoperation ot relay 12 also causes relay 13 to operate in an obviouscircuit. The master ringing key M having caused the operation of relays8, 13, and la can now be released at any time thereby causing therelease of relay 12 and the consequent release of relay G therebydisconnecting the master ringing circuit from the cord. Upon theoperation or' relay 14 prior to the release of relay 6 a locking circuitwas established for relay 13 which can be traced from grounded batterythrough the Winding of relay 13, its right hand alternate contact,conductor 32, inner lower alternate contact of relay 14, conductor 33,normal. contacts of relay 15, conductor 34, conductor and thence toground through the right hand alternate contacts ot relay 5. Relay 14 inoperating is also locked in a circuit which can be traced from groundedbattery, outer left alternate contacts of relay 4l, conductors 52 and36, winding or relay 14, inner lower alternate contact of relay 1d,conductor 33, normal contacts of relay 15', conductor 34, conductor 35to ground through the alternate contacts ot relay 5. Relay 13 inoperating, connects at its left hand alternate contact positivepulsating ringing current to the line over a path Which may be tracedfrom the current source G0 through the left hand winding of relay 15,normal contacts of relays 16 and 17, conductor 37, loivermost alternatecontact of relay 1e to the ring side of the cord and line and thenceover the line Where it will be assumed to cause the operation of theringer at sta tion M on the called line in a Well known manner.

It will be noted that the operation of relay 14 provides an auxiliaryshunt path to maintain the supervisory lamp dark when the original pathwas broken by the release ot relay 6. This shunt path may non' be tracedfrom grounded battery through the upper inner alternate contacts ofrelay 111 and resistance 11 through the lamp to grounded battery.

Automatic disconnection of ring/ng cn cdmadcnccl-calls and flcshzngrecall can. the mswcrrn-g cord.

In case the calling subscriber should hang up before the calledsubscriber answers, the following occurs: supervisory relay 7 willrelease, thereby releasing relay 1 and also breaking the shunt aroundsupervisory lamp 2 and allowing it to become lighted. Relay 4 inreleasing opens the circuit for relay le thereby dienen-neciting` the'ringing' eiirreiit Ltronifthe :called line.' VRelay M "i-n releasingopens the looking circuit :orfrelaygll 'which becomes lighted. uAutom/itin 'de'efcoii-iiectibii/V of ringing 012i/ answered alla v nothang up, the-antomatie ringing `will @persist iin-til the lcalledsubscriber answerer, at which time lrela-y livil-l operatevin 4the ice-lvlowing cir-cuit: positive :pulsating soiireetim' `leftalternatecontacteel'` relayl 13,-leiclt lifand Winding of relay lo, leftynormal.. contacts ,oft relay 16, inner lett normal-contacte.otrelaylglowerinost alternate contacts of relay le,

ring conductors 'of the cord andline -thrpugh the subscribere set,A tip.-feondiictorsof ,the line and oord, uppermost alternate contactsy ofrelay 14 to; groundfat t-hekouterk lett rmal contaetfoffrelay.17.; Relay15in .ener gizing opens at itsnornial.contactsthe lock ing circuitsfoi-' `relays l which relays release, thereby dieeenneetifnig theringing ourrent'fitroni the oordl. Si l the called subscriberanewersyand relay la releases, it will be noted that the ,Sh-ir t'around 'the calling -sii'peryisory lamp 8O opened kat the upper `inneralternate contacts or' relayfl4,`but the calling ,supei'yis'erfir 're-vlay 20 operates immediately over an eb us circuit fea-using relay 50 to-operateovt-ir an obvious pathythereby agaijn'shiinting the callingsupervisory lainp through. fgreiindedy .batt-ery over the vleftaltern-ate lcontante oit relay 50 and through resistance ll;` L

It will be observed that 'when ib-oth the calling and calledfsubscribershave tlir receiversolf the hook,

following circuit: groundedbattery`` lett' hand Winding of y relay 2l,righthand alter-A nate contacts of relay 4, altern-ate .Contacte `oirelay; 7, inner left, hand alternate centaeta y of relay. l togronndedbattery, and the. `right hand Winding being shuijited in acircuit which can be traced from grounded battery7 right hand Winding ofrelay 2l' 'and lettk vcirc-uit Atoi.relay Sie already breken at the'.

contacteer rel-ayl thereby preventing lvthe operator 'roinlisteningin ona conversation.

ln case either of the parties hangr up, the shunt around either` theleft `er ,the right nate oontaete oi relay 7, ri

hand Winding-of relay. will lajefreinoved due to thefreleaSe-of thevsupervisory relays 7 or 20,V astheeaee may be, thereby all-owingvrerated, a Circuit `whichextends from and 14; li'otlifotl y "lay 7opens .the-locking circuit :torrelay both the' left hand Vand f righthand windings of relay 21a-re sliiintetl,Ik the left hand AWinding beingShii'nted inr ythe` f4? 14 and 13 will bereleased and amper ne theodin-ally interrupted shunt cir relay to operate o a path avliichaean.beftracedft'rem Agiro'unded batteryi ilelit hand calling?Subeeriber*has hung yup;5.oi1oi1e-r a] path Vwhich can be traced #tronigrounded battery, right hand winding otrelay il icej ksistanee 1l,winding 'olE` relay and the e .n Ato ground on the sleeve ye'tstheitalled eufb-y Assuming that the calling subecriherdoes scribers line inonse the haal-ning up'.

rcalled' ibaeiibei' lf. at this` time `4`the listening "key 22 `is ,op-

"1nd, contacts onf-'relay121,*,iiernial contacte 'et :ltey 23 right handwindingof relay@ it'ogroundedbattery over thenorinal contacts oit relay3 will be completed vfor v.the oliierationof reacross "the cord;

Upon the completion g they-operatorie telephone ,i

't conversationyboth v subscribers will 'hang up, causing ythe release'oi"-"ielays -7 Aand 20; The release. ,of relay n 20 releases relayOvwhich removes the elmnt lroni around the l calling supervisory lampwhich becomes lighted andthe release of 're--y which in ,releasingopensthe int. .ciro around Supervisory l lamp 2, .thereby causing ittofvbeconie lighted. .l It willtherefore` he noted :that the.'calling.,eiipervisory lamp lis not `lighted until the calledSiibscrilier'lias answered and hung up. .This provides what is known asa dii-rk key Shelf feature;

. .lt will be noted that the windings of relay 21are ofahfighresis'tance -andxwill not p "i4 vide a low enough ,shuntpathtotezitingu .i either .of the superveory lla-inps..

:Let us now `:resume the coiidition where thefcalled subscribereitlierhas not answered the ring oirhae aneweredand` hung: up and thecalling'isubs'criber desires lit: recall the `operator before thecord-cire iit is then down.y ln Athev Case before described.. ,icalled-subscriber kdoes not.' newer, re.

lampeL 2, and 30 Willbeliggghted and the ingl current 'will bediseoniiec t 'l j fioin the called .line when the cal-ling au zrihe 1re.-

"placeshis receiver on the hook. Tlieae. saine relays Vwill relealeeanfdbothrlam-lpis will rhe lighted when a rfc.on\`-fereation iS completed.andboth .receivers` are hiing `iip. Non" Should tli'ecalling Subscriberdeeire to rec-all ythe operator before the cord cire-int ia taken down,he Willagain .rein-oneffhia. rece' f;

from the hooi: ythereby eau'e-ingrelay i again operated whichr willvconn te a i? l tnori'iial Qon-l tact-s 'otrelay @resistance liland tethe upper termmalneff Supervisar. lil-mii 2 thereby causing' this lampto flash in step with the interrupter 18 and give the operator what isknown asia flashing recall si gnal.

It the operator Wishes to extend a call to some distant operator inresponse to a toll order by the subscriber A, she will plug the callingend of her cord into trunk circuit T whereupon an energizing circuit isestablished which operates relay 5 over a path extending `from groundedbattery, filament ot lamp 30, winding of relay 5 and thence to groundover the sleeve of the trunk line. 1t will be noted that lamp 30 doesnot light in this circuit as it is shunted through resistance 11 togrounded battery at the outermost right hand alternate contacts ot relay6.

Then the operator plugs into the trunk line, she depresses the non-ringkey NR 'whereupon an obvious circuit't'or relay 40 is established. Relay40 non7 energizes and in operating closes its right hand alternatecontacts thereby establishing a circuit for relay 8 which can be tracedi'roin ground, right hand alternate contacts of relay all), contacts 25ot relay 6, conductor 26, normal contacts of relay 3 and thence togrounded batteryl throughr the Winding ot' relay 8.

The operation of relay 40 also causes relay 17 to energize and operatein a circuit Which can be traced from ground, lett hand alternatecontacts of relay 40, contacts 51 of relay 6, Winding otl relay 17,conductor 53, conductor 52 and thence to grounded battery over the outerlett alternate contacts of relay t. Relay 17 in operating closes itsinner right hand alternate contacts thereby locking itself over a pathextending from grounded battery at relay 4, left outer alternatecontacts ot relay l, conductor 52, conductor 53, Winding of relay 17,inner right hand contacts ot' relay 17, conductor 54, normal contactsot' relay 50, conductor 55 and thence to ground through the right handalternate contacts ot relay 5. Relay 8 in operating closes its righthand alternate contacts to form a locking circuit for itself whichextends from grounded bat-` tery, Winding ot' relay 8, right handalternate contact ot relay 8, conductor 35, and thence to ground overthe right hand alternate contacts ot relay 5 which relay remainsoperated during the time the calling plug is inserted in the jack ot'the trunk line. Relay 8 in operating also closes its inner left handalternate contacts to establish a holding circuit for relay 6 which canbe traced from grounded battery, Winding of relay 6, inner left handalternate contacts of relay 8, contacts 25 ot relay 6 and thence toground through contacts of relay 40. Relay S also breaks its outer lefthand normal contacts thereby causing the release of relay 3 which, inreleasing, disconnects the operators telephone set from the cordcircuit. lVhen the non-ringing key NR is released ground is disconnectedfrom the circuit for relay 40 as previously traced and thereforedeenergizes relays 40 and 6. 1t will be noted that relay 17 opera-tesand keeps the lamp 30 shunted When relay 6 releases. Relay G inreleasing obviously disassociates the master ringing key from the cordcircuit. lVhen the called subscriber at the distant end answers, relay2O energizes over an obvious circuit and in operating closes an obviouscircuit tor relay 50 to cause that relay t0 operate. Relay 50 inoperating opens the previously traced circuit for relay 17 therebycausing that relay to release. However, the operation of relay 5()holdsl lamp 30 shunted over an obvious circuit, even though relay 17releases thereby maintaining a dark'key shelf until the distant calledsubscriber has answered and hung up.

lVhat is claimed is:

1. A telephone system comprising telephone lines, an operators linkcircuit, a supervisory signal therein, means tor shunting said signalresponsive to the connection or said link circuit to a calling one otsaid lines, and means for maintaining said signal shunted until asubstation on a called one ot' said lines has responded and subsequentlyhangs up.

2. In a telephone system, a cord circuit tor interconnecting -a` callingand a called subscribers line, a called supervisory signal, a ringingcontrol relay for applying ringing current to the called line, a calledsupervisory relay, and means including said ringing control relay andsaid supervisory relay for maintaining said called supervisory signalunoperated until the called subscriber has answered and hung up. y

3. In a telephone system, acord circuit for interconnecting a callingand a called subscribers line, a called supervisory signal tor saidcalled line, a master ringing circuit control relay, a ringing controlrelay tor applying said ringing current to the called line, and a calledsupervisory relay, said relays successively acting during theestablishnient of a connection between said calling and said called lineto prevent said supervisory signal from being operated until the calledsubscriber has answered and replaced his receiver on the switchhook.

A telephone system comprising lines, a link circuit, means for applyingringing current to a called one of said lines, a supervisory signal, andmeans successively responsive to the connection or' said link circuit toa calling one of said lines, to the operation ol said ringing mea-ns andto the removal of the receiver at a station on said called line torcontinuously disabling said signal until the receiver at said calledstation is replaced on the switch hook.

5. A telephone system comprising lines,

` an operators linkciicuit, "a supervisory signal, means responsive vtoythe connection.

of' said link circiiitivitli a calling one or' said lines to disablesaidsignal, ringing means for signaling a substation on a called one of saidlines, ineans adapted to inaintain said signal disabled lduring theperiod. said called substation is being rung and until the receiverthereat is removed from the` hook, and afsuperviso'ry relay in said linkcircuit for further maintaining saidsignaly disabled until the receiverat the called sub? station is replaced onthe hook. n

6. A telephone system comprising telephone lines, an operators linkcircuit, a .su-- pervisoiy signal associated With the calling `end ofsaid linkfcircuit, a master ringing circuit arrangement tor signaling ona called one of said lines, and means includingk a relay operated whensaid link circuit is connected with a callingone of said lines toassocia-te said master. ringing circuit g'With said link circuit and todisable saidsupervisorysignal. c r

7. A telephone vsystem including a calling i and ak called linea klinkci cuit for interconnecting said lines, a supervisory signal,

a ringing key circuit, ineans operable upon `the connection of said linkcircuit `With a" calling one of said lincsfor associating said ringingkey circuit With said* link circuit and fordisabling said'supervisorysignal,

and other means including a ringing conf trol relay and a supervisoryrelay for maintaining said signal disabled until the sub-y scriber. on acalled one of said lines has answered and hung up. Y

8.` In a telephone system, i 'a calling and a called line, a linkcircuit for interconnecting said lines, a master ringing circuit andazringing control relay for applying ringing current to thecalled line,

a supervisory signal associated with ythe answering end of said cordkcircuit, means controlled by thedreplaceinent and subsen combination, f

receiverjtocause disconnection of said ringing current fromtliecalledline and to cause id supervisory signal n to bevintermittently ila lied, a supervisory relay and ,a second'suquentremoval of the .Calling Subscrberrs, a

perviscry signalassociated With the calling` a `master ringing circuitarrangement for signaling on the called line, ansvvering and callingksupervisory"signals associated with ftliejcoid circuit, means includinga relay i''or associating said ymaster 'ringing circuit withA said vcordcircuit and fordisabling the calling supervisoryfsignal when said cordrcircuit is connected With said calling line, means including a secondrelay operable in end of said cord circuit, ineans operable iip"- onthey connection oi` said cordcircuit ivithQ l said )calling-line rtoassociate said master ringing `circuit with said cord circuit and to 1'shunt said 'second supervisory signal, and

l response to. actuationoi said master ringing j arrangement toapplyfringing current, de#` in combination y termined by saidinasterwarrangeinent, fto

said called line when the calling end Asoif said'cordcircuit isassociated therewith and io `continue the disableinent of said callingand othermeans responsive to replacement called subscriber answer tocause disconnection of said ringing current` and removal of supervisorysignal.` .c c In Witness whereof, I yhereuntosubscribe v my naine this28th day of April A. D., 1924.

v a `RICHARD C. DAVIS.

suaervisor signal While rinOinO' continues y o zu. a: a a

said disabling condition from said calling of the ycalling subscribersreceiver beforethe v

